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Updated: Jun 21, 2026

Analysis of Cap-binding Proteins in Human Cells Exposed to Physiological Oxygen Conditions
Published on: December 28, 2016
The molecular basis for the regulation of the cap-binding complex by the importins
Sandra M G Dias1, Kristin F Wilson, Katherine S Rojas
1Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Abstract:
The binding of capped RNAs to the cap-binding complex (CBC) in the nucleus, and their dissociation from the CBC in the cytosol, represent essential steps in RNA processing. Here we show how the nucleocytoplasmic transport proteins importin-alpha and importin-beta have key roles in regulating these events. As a first step toward understanding the molecular basis for this regulation, we determined a 2.2-A resolution X-ray structure for a CBC-importin-alpha complex that provides a detailed picture for how importin-alpha binds to the CBP80 subunit of the CBC. Through a combination of biochemical studies, X-ray crystallographic information and small-angle scattering experiments, we then determined how importin-beta binds to the CBC through its CBP20 subunit. Together, these studies enable us to propose a model describing how importin-beta stimulates the dissociation of capped RNA from the CBC in the cytosol following its nuclear export.
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